Chapter 2 Brain and Behavior

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Chapter 2Brain and Behavior
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Neuron and Its Parts

• Neuron Individual nerve cell
• Dendrites Receive messages from other neurons
• Soma Cell body body of the neuron
• Axon Fiber that carries information away from
  the cell body
• Axon Terminals Branches that link the dendrites
  and somas of other neurons

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Figure 2.1
FIGURE 2.1 A neuron, or nerve cell. In the right
foreground you can see a nerve cell fiber in
cross section. The upper left photo gives a more
realistic picture of the shape of neurons. Nerve
impulses usually travel from the dendrites and
soma to the branching ends of the axon. The nerve
cell shown here is a motor neuron. The axons of
motor neuron stretch from the brain and spinal
cord to muscles or glands of the body.
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Synapses

• Messages from one neuron to another pass over a
  microscopic gap called a synapse
• Synapse Microscopic gap between two neurons over
  which messages pass

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Figure 2.5
FIGURE 2.5 A highly magnified view of a synapse.
Neurotransmitters are stored in tiny sacs called
synaptic vesicles (VES-ihkels). When a nerve
impulse reaches the end of an axon, the vesicles
move to the surface and release
neurotransmitters. These molecules cross the
synaptic gap to affect the next neuron. The size
of the gap is exaggerated here it is actually
only about one millionth of an inch. Some
transmitter molecules excite the next neuron, and
some inhibit its activity.
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Neurotransmitters

• Chemicals that alter activity in neurons brain
  chemicals
• Acetylcholine Activates muscles
• Dopamine Muscle control
• Serotonin Mood and appetite control
• Receptor Site Areas on the surface of neurons
  and other cells that are sensitive to
  neurotransmitters

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Nerves and Neurons

• Nerves Large bundles of axons and dendrites
• Myelin Fatty layer of tissue that coats axons
• Multiple Sclerosis (MS) occurs when myelin layer
  is destroyed numbness, weakness, and paralysis
  occur

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Neural Networks

• Central Nervous System (CNS) Brain and spinal
  cord
• Peripheral Nervous System All parts of the
  nervous system outside of the brain and spinal
  cord
• Somatic System Links spinal cord with body and
  sense organs controls voluntary behavior
• Autonomic System Serves internal organs and
  glands controls automatic functions such as
  heart rate and blood pressure

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Figure 2.6
FIGURE 2.6 (a) Central and peripheral nervous
systems. (b) Spinal nerves, cranial nerves, and
the autonomic nervous system.
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Two Divisions of the Autonomic System

• Sympathetic Arouses body emergency system
• Parasympathetic Quiets body most active after
  an emotional event

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Figure 2.8
FIGURE 2.8 Sympathetic and parasympathetic
branches of the autonomic nervous system. Both
branches control involuntary actions. The
sympathetic system generally activates the body.
The parasympathetic system generally quiets it.
The sympathetic branch relays its messages
through clusters of nerve cells outside the
spinal cord.
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The Spinal Cord

• Spinal Nerves 31 of them carry sensory and
  motor messages to and from the spinal cord
• Cranial Nerves 12 pairs that leave the brain
  directly also work to communicate messages

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Figure 2.7
FIGURE 2.7 Subparts of the nervous system.
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Figure 2.9
FIGURE 2.9 A sensory-motor arc, or re- flex, is
set in motion by a stimulus to the skin (or other
part of the body). The nerve impulse travels to
the spinal cord and then back out to a muscle,
which contracts. Such reflexes provide an
automatic protective device for the body.
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Researching the Brain

• Ablation Surgical removal of parts of the brain.
• Deep Lesioning A thin wire electrode is lowered
  into a specific area inside the brain.
  Electrical current is then used to destroy a
  small amount of brain tissue.
• Electrical Stimulation of the Brain (ESB) When
  an electrode is used to activate target areas in
  the brain.
• Electroencephalograph (EEG) Detects, amplifies,
  and records electrical activity in the brain.

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Figure 2.10
FIGURE 2.10 The functions of brain structures are
explored by selectively activating or removing
them. Brain research is often based on electrical
stimulation, but chemical stimulation is also
used at times.
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Researching the Brain (cont'd)

• Computed Tomographic Scanning (CT)
  Computer-enhanced X-ray image of the brain or
  body
• Magnetic Resonance Imaging (MRI) Uses a strong
  magnetic field, not an X-ray, to produce an image
• Functional MRI (fMRI) MRI that also records
  brain activity
• Positron Emission Tomography (PET)
  Computer-generated color image of brain activity,
  based on glucose consumption in the brain

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Cerebral Cortex

• Definition Outer layer of the cerebrum
• Cerebrum Two large hemispheres that cover upper
  part of the brain
• Corticalization Increase in size and wrinkling
  of the cortex
• Cerebral Hemispheres Right and left halves of
  the cortex
• Corpus Callosum Bundle of fibers connecting
  cerebral hemispheres

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Figure 2.21
FIGURE 2.21 The left and right brain have
different information-processing styles. The left
brain focuses on the small details the right
gets the big pattern.
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Split Brains

• Corpus Callosum is cut done to control severe
  epilepsy (seizure disorder).
• Result The person now has two brains in one
  body.
• This operation is rare and is often used as a
  last resort.

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Figure 2.19
FIGURE 2.19 Basic nerve pathways of vision.
Notice that the left portion of each eye connects
only to the left half of the brain likewise, the
right portion of each eye connects to the right
brain. When the corpus callosum is cut, a split
brain results. Then visual information can be
sent to just one hemisphere by flashing it in the
right or left visual field as the person stares
straight ahead.
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Figure 2.20
FIGURE 2.20 A circle is flashed to the left brain
of a split-brain patient, and he is asked what he
saw. He easily replies, A circle. He can also
pick out the circle by merely touching shapes
with his right hand, out of sight behind a
screen. However, his left hand cant identify the
circle. If a triangle is flashed to the patients
right brain, he cant say what he saw (speech is
controlled by the left hemisphere). He also cant
identify the triangle by touch with the right
hand. Now, however, the left hand has no diffi-
culty picking out the triangle. In other tests,
the hemispheres reveal distinct skills, as listed
above the drawing.
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Central Cortex Lobes

• Occipital Back of brain vision center
• Parietal Just above occipital bodily sensations
  such as touch, pain, and temperature
• Temporal Each side of the brain auditory and
  language centers
• Frontal Movement, sense of smell, higher mental
  functions
• Contains motor cortex controls motor movement

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Figure 2.22
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Figure 2.23
FIGURE 2.23 The lobes of the cerebral cortex and
the primary sensory, motor, and association areas
on each. The top diagrams show (in cross section)
the relative amounts of cortex assigned to the
sensory and motor control of various parts of the
body. (Each cross section, or slice, of the
cortex has been turned 90 degrees so you see it
as it would appear from the back of the brain.)
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Figure 2.25
FIGURE 2.25 This simplified drawing shows the
main structures of the human brain and describes
some of their most important features. (You can
use the color code in the foreground to identify
which areas are part of the forebrain, midbrain,
and hindbrain.)
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Forebrain

• Structures are part of Limbic System System
  within forebrain closely linked to emotional
  response
• Thalamus Relays sensory information to the
  cortex switchboard
• Hypothalamus Regulates emotional behaviors and
  motives (e.g., sex, hunger, rage, hormone
  release)
• Hippocampus Associated with storing memories

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Endocrine System

• Glands that pour chemicals (hormones) directly
  into the bloodstream or lymph system
• Pituitary Gland Regulates growth via growth
  hormone
• Too little means person will be smaller than
  average
• Hypopituitary Dwarfs As adults, perfectly
  proportioned but tiny
• Too much leads to giantism
• Excessive body growth

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Endocrine System (cont'd)

• Acromegaly Enlargement of arms, hands, feet, and
  facial bones
• Too much growth hormone released late in growth
  period
• Andre the Giant

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Endocrine System Concluded

• Pineal Gland Regulates body rhythms and sleep
  cycles.
• Releases hormone melatonin, which responds to
  daily variations in light.
• Thyroid In neck regulates metabolism.
• Hyperthyroidism Overactive thyroid person tends
  to be thin, tense, excitable, nervous.
• Hypothyroidism Underactive thyroid person tends
  to be inactive, sleepy, slow, obese.

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The Adrenal Glands

• Adrenals Arouse body, regulate salt balance,
  adjust body to stress, regulate sexual
  functioning located on top of kidneys
• Releases epinephrine and norepinephrine (also
  known as adrenaline and noradrenaline)
• Epinephrine arouses body is associated with fear
• Norepinephrine arouses body is linked with anger